1. Field of the Invention
The present invention relates to a tape cassette having a slider lock for a DDS (Digital Data Storage), a DAT (Digital Audio Tape), etc.
2. Related Background Art
A conventional tape cassette having a slider lock is disclosed in, e.g., Japanese Patent Application Laid-Open Publication No. 62-189687. An example of this prior art will be explained referring to FIG. 10. A body case 100 includes an upper case 100a and a lower case 100b. A bottom wall 400 of the body case 100 is provided with a shutter (slider) 101 in a slidable manner, and integrally with a lock member 190. An engagement portion 210 provided at a front side end 190a of the lock member 190 engages with an engagement hole 310 of the shutter 101. A coil spring 220 for biasing the front side end 190a downward in FIG. 10 is disposed between an inner surface of the upper case 100a and an upper surface of the front side end 190a of the lock member 190. The coil spring 220 presses downward the engagement portion 210 of the lock member 190, thereby locking the shutter 101. Incidentally, upon a release from the locking by the engagement portion 210 of the lock member 190, the shutter 101 slides leftward in FIG. 10, and similarly engages with an engagement hole 300 and is thus locked.
FIG. 11 shows a slider lock structure disclosed in Japanese Patent Application Laid-Open Publication No. 63-34478. This slider lock structure is that a lock member 160 is pressed downward in FIG. 11(a) by a spring arm 221 of a plate spring 211 attached while being bent in an L-shape to a cylindrical tape guide 70 of a lower case 100b, thus locking. The plate spring 211 is held such that a fitting portion 230 is inserted into a groove 300 formed in the tape guide 70. In this case, as illustrated in FIG. 11(b), the fitting portion 230 is formed with an elastic engagement member 270 which overhangs and is fitted by pressure into the groove 300.
FIG. 12 shows another slider lock structure disclosed in Japanese Patent Application Laid-Open Publication No. 4-57264. As shown in FIG. 12(a), a plate spring 201 secured by welding in the vicinity of the center of a lower case 100b extends in a cantilever type to a lock member 161 on sides of side ends of the case, and the lock member 161 is pressed by front side ends 202 of the plate spring 201 in a rear-side direction on the sheet surface, thus locking it.
According to the prior art shown in FIG. 10, however, the coil spring 220 is unable to exhibit its effect unless the upper and lower cases 1001, 100b are assembled. Therefore, the slider is biased forward by the slider spring. If the locking force is insufficient, there might be a possibility of causing such a trouble that the slider comes off in the assembly process. Further, the coil spring 220 exists in a whole-thicknesswise direction of the inner surface of the case 100, and hence, if the tape slackens, there might be a possibility in which the tape comes into contact with the coil spring 220. Moreover, the prior art coil spring is provided with a narrow-pitch portion in the spring element in order to prevent the spring wires from entangling with each other. This leads to an increase in quantity of materials to be used and a rise in manufacturing costs as well.
Further, according to the prior art shown in FIG. 11A, the structure for fitting and holding the plate spring 211 to the tape guide is complicated, and therefore the structure of the plate spring 210 becomes also complicated as seen in the fitting portion 230 having the elastic engagement member 270 as shown in FIG. 11B. Therefore, the plate spring is formed with a difficulty, resulting in a rise in the manufacturing costs.
Moreover, according to the prior art shown in FIG. 12A, the plate spring 201 is fitted to the case by welding, and hence, the number of assembling processes increases, which leads to the increase in the manufacturing costs. Further, as shown in FIG. 12B, a welding portion 222 of the plate spring 201 is formed in swelling and consequently the spring protrudes from the inner surface of the case, with the result that an adverse influence is exerted on running of the tape. Moreover, the lock members 161 are pressed by the front side ends of the plate spring 201 in the cantilever type, and hence the front side ends 202 become free, whereby a quantity of deformation augments. Therefore, the plate spring protrudes from the inner surface of the case, and there might arise a possibility of exerting the adverse influence on the running of the tape.
It is a primary object of the present invention to provide a tape cassette having a slider lock and capable of enhancing an assembling characteristic with a construction in which a locking force acts even when assembling cases and a slider does not come off during an assembly process.
It is another object of the present invention to provide a tape cassette having a slider lock with such a construction that a spring for the slider lock does not protrude toward an inner surface of the case in states of being fitted and deformed, and does not come into contact with a tape.
It is a further object of the present invention to provide a tape cassette having a slider lock, which is capable of reducing costs for parts and manufacturing costs, wherein a spring for the slider lock is simply structured.
To accomplish the above objects, according to a first aspect of the present invention, a tape cassette comprises a case body including an upper case and a lower case, a recessed portion formed on the side of a lower surface of the case body, a slider so provided in the case body as to be slidable for opening and closing the recessed portion, a lock member positioned at an opening of the lower case to lock the slider in respective positions where the recessed portion is closed and opened, and a biasing member, supported at its two side ends with the opening being interposed therebetween by an inner surface of the lower case, for biasing the slider to a lock position.
In this tape cassette, the biasing member is provided on the side of the lower case, and hence, before being assembled integrally with the upper case, the slider can be surely locked. This locking force prevents the slider from coming off in the assembly process, resulting in an enhanced assembling characteristic. Further, the biasing member supported on both sides with the opening being interposed therebetween biases the lock member positioned at the opening to a non-lock position. Therefore, even when the lock member moves to the non-lock position, resisting the biasing force of the biasing member when unlocked, the biasing member neither protrudes from the inner surface of the case with no particular deformation nor comes into contact with the tape-shaped member within the case body. The tape-shaped member is wound on peripheries of a pair of hubs provided within the case body.
Further, the biasing member may be constructed, when the lock member is in the locking state, so as not to protrude from the inner surface of the lower case. With this construction, when locking by the lock member, the biasing member neither protrudes from the inner surface of the case nor comes into contact with the tape-shaped member.
Support members for supporting the biasing member may be provided on both sides of the opening of the inner surface of the lower case. Based on this configuration, the biasing member is supported by the support members at both ends of the opening and can therefore be attached with a stability to the inner surface of the lower case.
The lock member may have a protruded portion engaged for locking the slider, and the biasing member may be provided in a position corresponding to the protruded portion. The biasing member thereby surely biases the lock member.
The biasing member may be constructed in the form of a plate spring or a wire spring. This makes it feasible to attain a simple configuration of the biasing member and reductions both in the costs for the parts and in the manufacturing costs. Further, when in locking and unlocking of the lock member, the biasing member neither protrudes from the inner surface of the case nor is brought into contact with the tape-shaped member.
The biasing member may be so disposed as to be substantially orthogonal or inclined to the lock member.
According to a second aspect of the present invention, a method of manufacturing a tape cassette by assembling a plate spring as a biasing member into a lower case, comprises a step of making a holding member close to an inner surface of the lower case in a state of holding the plate spring, a step of inserting at first two side ends of the plate spring and the plate spring itself into through-holes of the lower case, a step of making an insertion member proximal to an outer surface of the lower case in a direction opposite to the spring, a step of letting, after the holding member has become very proximal to the inner surface of the lower case, the two side ends of the plate spring pass through the through-holes and the plate spring penetrate therethrough on the side of the outer surface of the lower case, a step of making the insertion member close from the side of the outer surface and receive the two side ends of the plate spring, a step of making the insertion member enter into the through-holes to push the plate spring at the two side ends, and a step of making a release from the holding by the holding member, and pressing the plate spring by a pressing member of the holding member with the result that the two side ends of the plate spring enter in a stretched manner the inner surface of the lower case. Thus, the plate spring can be assembled by pressing the plate spring in two directions.
According to the above method of assembling the plate spring into the lower case, the plate spring can be simply assembled at the respective support member, which can contribute to the reduction in the manufacturing costs. Note that the wire spring classified as the wire member can be similarly assembled instead of the plate spring.